One of the "rules" of 1980s slasher films is that every film ends with a "last girl," a tradition begun by Jamie Lee Curtis in John Carpenter's Halloween (1978). Yet a number of films break this rule.
Warning: Spoilers ahead.
Consider Pranks (aka, The Dorm That Dripped Blood). Very low budget. Four college kids (count 'em, just four!), at an deserted college campus. Two guys, two gals. The campus is deserted because the kids are closing it up for the winter break.
Okay, there's a fifth student, Daphne Zuniga (the Last Girl in The Initiation), but Zuniga dies early in this film (nicely run over by a car), along with her parents. Then two other college kids (and the red herring suspect) are killed over the next hour.
That leaves the Last Girl with another kid who turns out to be the psycho killer. There was no reason to suspect him, it's all arbitrary, but that's common and appropriate for horror films, albeit not for mysteries. Mysteries require clues so the audience may guess the killer; horror is about fear, not a puzzle, and a threat is all the more fearsome if its identity is unknowable.
Then this psycho kills the Last Girl. He also successfully fools the cops, so he gets off. We know he'll be out there killing again.
Then there's Hide and Go Shriek. Eight high school kids celebrate their graduation by hiding out in a furniture store for sex and hijinks. They can do this because one of their dads owns the store, Fine Furniture. (This is similar to the kids hiding out in the mall in The Initiation, because, you guessed it, Daphne Zuniga's dad owns the mall.)
The killer in Hide and Go Shriek turns out to be a cross-dressing gay. Probably a less likely villain in today's more PC climate, but standard for the time. What's remarkable about Hide and Go Shriek is that four of the eight students (two guys and two girls) survive!
That's right. Eight potential victims, and fully half of them survive. Yes, there are some incidental victims, but four survivors does not make for a very generous body count. Still, Hide and Go Shriek is entertaining, in that "1980s low budget slasher" sort of way.
And there's also Intruder, a very nice film about grocery clerks closing up a store that's about to be sold and torn down. Not only does the killer survive, but so do two of the kids -- the potential Last Girl (Elizabeth Cox) and her ex-boyfriend -- who are then falsely arrested for the murders. As in Pranks, the cops are fooled.
Again, this is appropriate for horror, if not for mysteries. The latter genre seeks order, while the former creates fear by disrupting that order. If the cops are inept, the world becomes a more fearsome place.
Intruder features Renée Estevez, who also appears in Sleepaway Camp II: Unhappy Campers. Estevez is sister to Emilio Estevez and Martin Sheen, daughter of Martin Sheen.
All the the above films are recommended for hardcore horror fans. By "hardcore," I mean "forgiving." Only a forgiving, hardcore fan would enjoy some of the above ultra-low budget fare, Pranks being the lowest budgeted.